U.S. patent number 4,633,632 [Application Number 06/670,472] was granted by the patent office on 1987-01-06 for structural component having a curved wall and apparatus for making such structural component.
This patent grant is currently assigned to Messerschmitt-Boelkow-Blohm Gesellschaft mit beschraenkter Haftung. Invention is credited to Branko Sarh.
United States Patent |
4,633,632 |
Sarh |
January 6, 1987 |
Structural component having a curved wall and apparatus for making
such structural component
Abstract
A structural component having a curved wall, such as an aircraft
fuselage pipe, has a grid structure formed of box frames produced
by winding tapes of fiber reinforced synthetic material, so-called
prepregs, onto mold bodies. These mold bodies are then assembled on
a mandrel for covering with a planking and curing whereby the tapes
are bonded together to form stringers intersecting with ribs in a
grid structure and whereby the planking is bonded to the grid
structure. The ribs are reinforced by fiber reinforced belt
segments of synthetic material inserted into gaps between adjacent
short ends of the mold bodies, whereby these belt segments are
bonded to the ribs during curing. The belt segments have a width
corresponding to a multiple of the width of the stringers and hence
protrude radially inwardly. Preferably, an edge reinforcing strip
of fiber reinforced material is arranged alongside the radially
inner edge of the belt segments. The mandrel carries support rings
which are axially displaceable along the mandrel and which carry
mold body support plates by radially adjustable members for placing
the support plates into a plurality of different positions for
assembling, curing and mold body removal.
Inventors: |
Sarh; Branko (Watertown,
MA) |
Assignee: |
Messerschmitt-Boelkow-Blohm
Gesellschaft mit beschraenkter Haftung (Munich,
DE)
|
Family
ID: |
6214554 |
Appl.
No.: |
06/670,472 |
Filed: |
November 9, 1984 |
Foreign Application Priority Data
|
|
|
|
|
Nov 17, 1983 [DE] |
|
|
3341564 |
|
Current U.S.
Class: |
52/245;
52/84 |
Current CPC
Class: |
B29C
53/70 (20130101); B29C 70/342 (20130101); B64C
1/12 (20130101); B21J 15/142 (20130101); B29C
70/446 (20130101); Y02T 50/43 (20130101); Y02T
50/40 (20130101); B29C 2791/001 (20130101) |
Current International
Class: |
B29C
53/70 (20060101); B29C 53/00 (20060101); B29C
70/04 (20060101); B29C 70/44 (20060101); B29C
70/34 (20060101); B64C 1/12 (20060101); B64C
1/00 (20060101); E04C 002/36 () |
Field of
Search: |
;52/245,309.1,309.8,807,728,84 ;244/119 ;428/116 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Bell; J. Karl
Attorney, Agent or Firm: Fasse; W. G. Kane, Jr.; D. H.
Claims
What is claimed is:
1. A structural component having a curved wall with a longitudinal
axis, comprising longitudinal stringers (20) extending
substantially in parallel to said longitudinal axis and having a
given width in a direction toward said longitudinal axis and ribs
(28) extending substantially perpendicularly to said stringers (20)
and circumferentially relative to said longitudinal axis for
forming a grid structure, planking means covering said grid
structure, said ribs, stringers and planking means being made of
fiber reinforced synthetic material and bonded to one another, said
ribs further comprising reinforcing belt segments (28) also made of
fiber reinforced synthetic material and having a width dimension in
the direction toward said longitudinal axis corresponding to a
multiple of said given width dimension of said stringers for
forming radially extending flanges for reinforcing the respective
rib, wherein said ribs and stringers comprise preimpregnated bands
of fiber reinforced synthetic material forming rectangular box
frames having longitudinal sides and short ends assembled in an end
to end and side by side fashion for forming said grid structure,
first means bonding said longitudinal sides to each other to form
said stringers, and second means bonding said short ends to each
other to form said ribs.
2. The structural component of claim 1, wherein said rib
reinforcing belt segments are interposed between adjacent box frame
ends forming said ribs.
3. The structural component of claim 1, wherein said rib
reinforcing belt segments are multilayer belts of fiber reinforced
synthetic material.
4. The structural component of claim 1, wherein said rib
reinforcing belt segments comprise an edge reinforcing strip of
fiber reinforced synthetic material along its edge below the
respective rib.
5. The structural component of claim 1, wherein said stringers have
an I-cross-sectional configuration including a web between a
radially outer flange covered by said planking and a radially inner
flange, said stringers further comprising tapes of fiber reinforced
material bonded to at least said radially inner flange for
reinforcing said radially inner flange of said stringers.
6. The structural component of claim 1, wherein said planking is a
substantially seamless skin having a shape of a body of rotational
symmetry relative to a rotational central axis.
7. The structural component of claim 1, wherein said planking
comprises a helically wound webbing strip of fiber reinforced
material bonded to said stringers and ribs.
8. The structural component of claim 1, wherein said planking
comprises a plurality of elongated webbing strips arranged in
longitudinal overlap relative to one another.
9. The structural component of claim 1, wherein said planking
comprises openings therein, and layers of fiber reinforced
synthetic material surrounding said openings.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
The present invention relates to the disclosure of U.S. Ser. No.
540,705, now U.S. Pat. No. 4,524,556 filed on Oct. 11, 1983, as an
FWC of U.S. Ser. No. 228,680, filed on Jan. 26, 1981. The present
disclosure is also related to U.S. Ser. No. 544,112 now U.S. Pat.
No. 4,512,837, issued on Apr. 23, 1985, filed on Oct. 20, 1983 as a
CIP of U.S. Ser. No. 540,705 now U.S. Pat. No. 4,524,556, issued on
June 25, 1985.
FIELD OF THE INVENTION
The invention relates to a structural component having a curved
wall such as an aircraft fuselage or a pipe. The invention also
relates to an apparatus for making such curved wall structural
components.
DESCRIPTION OF THE PRIOR ART
Large structural components such as an aircraft wing have been
constructed heretofore in accordance with the disclosure of the
above mentioned two U.S. Patents of fiber reinforced synthetic
material formed into longitudinally extending stringers and
crosswise extending ribs forming a grid structure covered also by a
fiber reinforced synthetic material planking. The grid structure is
formed from box frames produced by a winding or bandaging method.
The so produced box frames are then assembled to form the large
wall or surface and to cure the box frames, whereby the
longitudinal side portions of two adjacent box frames form the
longitudinal stringers and the end portions of two adjacent box
frames form the ribs, all bonded together as a result of the
curing. The planking is also bonded to the grid structure as a
result of the curing.
Structural components of fiber reinforced materials constructed as
mentioned above, are statically equivalent to respective sheet
metal structures which thus can be replaced by fiber composite
material structures of substantially reduced weight, yet of
comparable size. By suitably designing and manufacturing such
components of fiber composite material, it is further possible to
reduce the manufacturing costs by providing for a single heat
compression curing operation in which as many elements as possible
of a large structural component are bonded to each other
simultaneously while they are being cured.
The above mentioned related U.S. Pat. Nos. 4,512,837 and 4,524,556
disclose such a large scale structural component comprising an
outer skin forming the planking on an inner grid structure forming
a stiffening frame. The outer skin or planking is first formed
apart from the grid structure inside a gluing or bonding apparatus
by laminating fiber webbings impregnated with a synthetic material,
so-called prepregs, onto a separate support. The grid structure
itself also is manufactured in a separate apparatus by assembling
rectangular mold bodies, to the side and end surfaces of which the
prepreg tapes or webbing strips have already been applied by a
winding or bandaging operation, into a substantially flat grid
structure which is then compressed in the longitudinal and cross
directions for the bonding of the prepregs to each other to form
the longitudinal stringers and the crosswise extending ribs. The
scaffold or support which holds the so formed grid structure is
then lowered onto the prelaminated planking in the gluing apparatus
and the entire combination is cured in a hot pressing
operation.
Structural components produced as just described are essentially
flat and, depending on their shape, they may be used as floor
elements, wings, tail unit shells including rudder and/or elevator
unit shells. The required curvature for these shells is provided by
the outline or so-called sheer of the respective component which in
turn is accomplished by a respective shape of the mold bodies. The
just described manufacturing operations and devices are not
suitable for making aircraft fuselages and the like, for example
large diameter pipe sections.
OBJECTS OF THE INVENTION
In view of the foregoing it is the aim of the invention to achieve
the following objects singly or in combination:
to construct a structural component having a curved wall in such a
manner that it may be used for assembling an entire aircraft
fuselage or pipe section, or the like;
to construct an aircraft fuselage or other substantially
cylindrical body of box frames made of fiber reinforced synthetic
materials in such a way that substantially all of the elements may
be in their still uncured condition when they are assembled, so
that the entire fuselage and thus all its components are cured
simultaneously in a hot pressing operation;
to provide an apparatus for manufacturing such large scale
three-dimensional bodies, whereby the box frame assembly, the
laminating of the planking onto the box frames, and the mold body
removal may all take place in the same apparatus; and
to construct the apparatus in such a way that it may itself
function as the pressurizable container or so-called autoclave so
that separate large scale autoclaves are not necessary anymore.
SUMMARY OF THE INVENTION
According to the invention the structural components are
constructed with rib reinforcing belt segments also made of fiber
reinforced synthetic material and having a width dimensioned
corresponding to a multiple of a width dimension of the above
mentioned stringers for reinforcing the respective rib. Preferably,
the rib reinforcing belt segments are themselves also reinforced by
an edge strip of fiber reinforced synthetic material running along
the edge of the belt protruding below the respective rib radially
inwardly.
The apparatus according to the invention is so constructed that
groups of mold bodies are arranged around the circumference of a
wheel rim type ring which itself is supported on a mandrel while
carrier plates for the individual mold bodies are secured to the
outer circumference of the wheel rim ring by means of radial drives
such as hydraulic cylinders and by means of radial guides such as a
cylindrical rod guided in a guide bushing. The arrangement is such
that the carrier plates and thus the mold bodies are radially
adjustable by the radial drives. A plurality of wheel rim rings are
provided which are supported on the mandrel by longitudinal or
axial guide rails for locating the wheel rim rings in the axial
direction along the mandrel. Thus, by the radial adjustment of the
carrier plates and mold bodies it is possible to assemble the mold
bodies into a position in which they define the cylindrical body to
be formed. On the other hand, the locating of the wheel rim rings
in the axial direction makes it possible to provide initially a
certain gap between adjacent mold body ends for inserting the above
mentioned rib reinforcing belt segments which are then compressed
between two short ends of longitudinally adjacent mold bodies for
the subsequent curing and bonding. In this manner very large scale
tubular bodies may be formed.
Another advantage of the invention is seen in that the structural
features of the invention enable a large scale automation of the
manufacturing steps, whereby the assembly of the entire structural
component such as an aircraft fuselage can be accomplished with
prepreg layers which have not yet been cured or hardened and so
that the hardening of all the elements of the component can take
place simultaneously in a hot pressing operation, whereby a
structural component may be made as a seamless cylinder or a
seamless conical shape. Sectional shells of this type may also be
manufactured separately and then connected to each other along a
seam.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be clearly understood, it will now
be described, by way of example, with reference to the accompanying
drawings, wherein:
FIG. 1a is a perspective view of a mold body according to the
invention;
FIG. 1b shows a perspective view of the mold body of FIG. 1a in its
disassembled condition;
FIG. 1c shows a top plan view of a fiber reinforced synthetic
material prepreg webbing or tape to be wound around the mold body
for forming box frames;
FIG. 1d shows a schematic perspective view of a mold body with the
prepreg tape or webbing wound around the side and end surfaces of
the mold body prior to the folding of the edges;
FIG. 1e shows a sectional view along section line e--e in FIG. 1,
however, after the folding of the longitudinal edges;
FIG. 1f shows a sectional view along section line f--f in FIG. 1d,
however, after the folding of the top edges along the short ends of
the mold body;
FIG. 2 is a sectional view in a plane extending perpendicularly to
the central longitudinal axis in FIG. 4, and employing mold bodies
as shown in FIGS. 1a and 1b, only three mold bodies are shown;
FIG. 3 is a partial sectional view through an assembly along a
plane extending longitudinally through the central axis of the
tubular structural component shown in FIG. 4;
FIG. 4 shows a perspective view of a supporting mandrel structure
forming part of the present apparatus for manufacturing structural
components as disclosed herein;
FIG. 5 shows a perspective view of the entire manufacturing
apparatus according to the invention employing a mandrel as shown
in FIG. 4; and
FIG. 6 is a perspective view into a portion of a tubular component
of the invention with some of the mold bodies already removed and
with further mold bodies yet to be removed.
DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE
BEST MODE OF THE INVENTION
FIGS. 1a and 1b show a mold body 1 including a central mold member
2 having two longitudinal walls tapering substantially radially
outwardly so as to converge radially outwardly relative to a
central longitudinal axis A shown in FIG. 4. The mold body further
comprises two lateral mold members 3 and 4 each having a first
longitudinal wall facing inwardly toward the tapering walls of the
central mold member 2 and having a taper corresponding to the first
mentioned tapering, whereby the withdrawal of the central mold
member 2 radially inwardly relative to said central axis A is
facilitated as will be described in more detail below. Each of the
lateral mold members 2 and 3 also has a second longitudinal wall
facing outwardly away from the central mold member 2. In the
assembled condition shown in FIG. 1a the longitudinal, outwardly
facing surface areas 12a, 12b together with the short end surfaces
12c and 12d form a continuous frame type mold surface for carrying
tapes of fiber reinforced synthetic material in the form of
so-called prepregs which are wound around the frame type mold
surfaces 12a to 12d in a conventional winding or bandaging
operation. All surfaces contacted by the prepregs are first
conventionally coated to prevent sticking. The forward facing end
of the mold body is supported by a rib bracket 5. The rearward
facing end of the mold body is supported by a second rib bracket
5a.
A plurality of such mold bodies 1 as just described, are assembled,
after the conventional winding or bandaging operation is completed,
in an apparatus as will be described below. In their assembled
condition the mold bodies define the curved wall and as a result of
the curing, the stiffening grid structure and the outer planking
are bonded to each other. In the assembled condition all the mold
bodies are located in a three-dimensional coordinate system x, y,
and r, as shown in FIG. 1a, whereby the x direction extends in
parallel to the central longitudinal axis A shown in FIG. 4,
whereby the r direction is the radial direction relative to said
longitudinal axis A, and wherein y is the circumferential
direction, for example, of a cylindrical fuselage section, or
rather the tangential direction.
As seen in FIG. 1b, the forward rib bracket 5 is a separate
component which is connected to the mold members 2, 3 and 4 by
conventional means, for example, snap-in members symbolically shown
at 11. On the other hand, the rear rib bracket 5a is formed by
three integral, one piece extensions 6, 7, and 8 of the mold
members 3, 2, and 4, as shown in FIG. 1b. These extensions 6, 7,
and 8 together form the rear rib bracket 5a when the mold members
and brackets are assembled as shown in FIG. 1a. Both rib brackets 5
and 5a protrude slightly in the longitudinal direction to an extent
"s" as shown in FIG. 1a and also in FIG. 3. The spacing "s"
accommodates the tape when it is wound around the surfaces 12a to
12d. The rib bracket 5 has a recess 9 while the rib bracket 5a has
a shoulder 10 on which the lower end of the rib bracket 5 may rest
in the assembled condition as shown in FIG. 3. The recess 9 is
provided for a rib reinforcement to be described below.
Incidentally, the longitudinal mold members 2, 3, and 4 are also
interconnected by conventional snap-in elements 11, whereby the
mold members are easily attached to each other and released from
each other.
FIG. 1c shows a tape or prepreg strip 61 provided with cut-outs 62
at spaced intervals along one edge thereof and with slots 63
opposite the cut-outs 62. The tape 61 of fiber reinforced synthetic
material which is not yet cured is then conventionally wound around
the mold body 1 so that the tape covers the surfaces 12a, 12b, 12c,
and 12d as shown in FIG. 1d. The width 64 of the tape 61 is larger
than the width of the walls 12a to 12d so that the edges of the
tape protrude above and below the mold body 1 except at the
downwardly facing end edges where the cut-outs 62 are located, also
as shown in FIG. 1d. After the winding operation is completed, the
edges or margin of the tapes 61 are folded over as shown in FIGS.
1e and 1f. After the assembly of the wound mold bodies to form the
curved wall of the structural component and after the curing of the
fiber composite material of the tapes 61, the mold bodies are
easily removed from the resulting grid structure due to the
cut-outs 62 which permit moving the central mold member 2
downwardly or radially inwardly as indicated by the arrow 65 in
FIG. 1f, after the mold member 5 has been removed. After the
central mold member 2 has been removed, the lateral mold members 3
and 4 are moved inwardly toward each other and down in the
direction of the arrow 65. This removal of the mold body from the
finished structure is greatly facilitated by the longitudinal
division of the mold body into three mold members 2, 3 and 4 and by
the radially outwardly converging side walls of the central mold
member 2. The mold members 2, 3, and 4 form with their top surface
13 a curvature in accordance with the curvature of the fuselage.
Thus, during the curing of the assembly, the planking rests on the
curved surface 13 and thereby assumes the required curvature. The
surface 13 is surrounded by grooves 14, 15, 16 and 17 adjacent the
edges of the mold body. These grooves provide space into which the
margins of the tape 61 are folded as shown in FIGS. 1 e and 1f.
Corresponding grooves not visible in FIG. 1a are also provided
along the longitudinal, downwardly facing edges of the mold bodies
3 and 4. As mentioned above, the end surfaces 18 and 19 of the rib
brackets 5 and 5a project by the distance "s" in the longitudinal
direction to provide the space needed for the rib forming tape
portions above the cut-outs 62. The size of the spacing "s" will
depend on the number of prepreg strips 61 to be wound around the
mold body 1. Normally, several windings will be employed to form a
multilayered box frame. However, even a single layer may be used
under certain circumstances, for example, where smaller bodies are
involved.
FIG. 2 shows a partial sectional view through an apparatus for
constructing an aircraft fuselage, whereby the section plane
extends perpendicularly to the longitudinal axis A in FIG. 4, and
whereby the view direction extends in the direction of the axis A.
Only three form bodies are shown in their full section in FIG. 2,
while the form bodies to the left and right are shown broken away.
According to the here employed division, for example, a total of
ninety-six mold bodies 1 are distributed around the circumference
of the fuselage, thereby forming ninety-six stringers 20 having an
I-beam cross-sectional shape and extending in parallel to the
longitudinal axis A. Due to the bonding of adjacent tapes to each
other which initially have a U-configuration, the resulting
stringers 20 have a radially extending double web section 21 and a
radially outwardly located flange section 22, as well as a radially
inwardly located flange section 22a. The radially outer top surface
13 of all the mold bodies is covered by a planking 55 applied as
will be described below.
The mold bodies 1 are supported on carrier plates 23 in a
conventional manner, for example, the carrier plates 23 may be
provided with a plurality of plug-in pins not shown, but reaching
with a slight press fit into respective holes 67 shown in FIG. 6.
Each carrier plate 23 is supported by a radially adjustable piston
cylinder device 24 which in turn is secured to a wheel rim type
ring 36 forming part of a central mandrel to be described below
with reference to FIG. 4. Each carrier plate 23 is further
supported by at least one radial guide device, such as a guide
bushing 31 in which a guide rod 31' is radially slidable. Two guide
bushings 31 are shown in FIG. 2 for convenience of illustration.
However, in actuality, these guide bushings would be located in a
plane in front of or in a plane behind the plane defined by the
sheet on which FIG. 2 is shown. The radial adjustment devices 24 do
not need to be piston cylinders. Any type of drive, for example, a
rack and pinion drive, may be used to bring the carrier plates 23
into three defined positions 25, 26, and 27 as shown in FIG. 2. The
carrier plates have longitudinal edges 23' of a reduced thickness
and facing alternately up or down for a sliding cooperation with
adjacent carrier plates 23 as these plates are moved radially
between the positions 25, 26, and 27. In the radially outermost
position 25, which may be defined by stops not shown, the carrier
plates 23 are sufficiently spaced from one another around the
circumference of the fuselage to be formed, whereby mold bodies
with the tape wound around the mold bodies may be conveniently
attached to the carrier plates 23 so that a gap 60 is formed,
extending longitudinally substantially in parallel to the central
axis A. When all the mold bodies have been attached to the carrier
plates 23, the latter are moved radially inwardly into the position
26, whereby the web sections 21 contact each other for the curing
and resultant bonding to be described in more detail below. The
grid structure so formed remains in the position 26 when, after
curing, the central mold members 52 and the lateral mold members 3,
4 are removed from the grid structure. At that time the carrier
plates 23 have been moved radially inwardly into position 27 and
out of the structural component, as will be described below.
As also shown in FIG. 2, the rib support brackets 5 and 5a are
provided with cut-outs 70 for the application of reinforcing strips
56 of fiber compound material which are bonded to the flanges 22a
of each stringer 20 with the aid of a tool 57 to be inserted into
the cut-outs 70 and held therein by a bracket 57' pressing the tool
57 and thus the respective strips 56 in place during the curing and
bonding. Similarly, a strip 58 is attached to the radially outer
flanges 22 prior to the application of the outer planking 55.
FIG. 3 shows a side view substantially in the circumferential
direction, whereby four mold bodies 1a, 1b, 1c and 1d forming
stringers are visible, and whereby the mold bodies 1b and 1c are
interrupted so as to fit them onto the sheet and not to show their
entire length LF. Further, the right-hand end portion of the mold
body 1b and the left-hand end portion of the mold body 1c are shown
in section for explaining the insertion of rib reinforcing belt
segments 28 which extend circumferentially around the fuselage in
the ribs. For this purpose adjacent mold bodies are spaced
initially from one another in the longitudinal direction to form a
gap BSL for said insertion of the rib reinforcing belt segments 28
of fiber composite material. After such insertion the adjacent mold
body is moved into contact with the inserted belt segment 28,
whereby the gap BSL is removed for the bonding and curing. Only one
carrier plate 23 is shown in its full length in FIG. 3 in the
radially inward position 27. These carrier plates are movable in
the axial direction along guide rails 35 carrying the radial
adjustment cylinders 24 and the radial guide members 31 as
described above with reference to FIG. 2. By radially positioning
the carrier plates 23 the gap BSL can be closed.
The rib reinforcing belt segment 28 as shown in FIG. 3 has a web
section 29 and an edge reinforcing strip 30 also of fiber
reinforced synthetic material extending circumferentially and
radially inwardly of the grid structure as best seen in FIG. 6.
Thus, these reinforcing strips 30 are located below the respective
rib formed by two circumferential flanges 66 and the respective
tape portions 61. Said belt segment 28 with its web section 29 and
its reinforcing strip 30 forming a radially extending flange,
especially a radially inwardly extending flange. However, the web
section 29 of the belt segment 28 reaches between the rib forming
tape portions 61. Each of the rib reinforcing belt segments 28 has
a length, in the circumferential direction, which is slightly
larger than the respective width of the mold body so that segments
28 of adjacent rib sections overlap each other in the
circumferential direction to form a closed ring inside the rib
sections. Preferably, the circumferentially protruding ends of the
segments 28 are tapered at an angle of about 1.5.degree. to provide
a splicing type of overlap joint between circumferentially adjacent
segments 28. Further, due to the above described shape of the rib
brackets 5 and 5a with the recess 9 and the shoulder 10, the
segments 28 are supported entirely on all sides, except the
radially outer edge when the two adjacent mold bodies are moved
together in the axial direction. Thus, after curing the rib
reinforcing segments 28 will have the respective cross-sectional
shape, see FIG. 3.
FIG. 4 shows a perspective view of the mandrel or arbor 32a for
supporting the mold body carrier plates 23. The arbor 32a is
constructed as a truss work forming a cage, whereby the truss
components are made of, for example, tubular steel sections having
a rectangular cross-sectional shape. The cage comprises a central
shaft 32b and eight axially outer longitudinal beams 33 connected
to the central shaft 32b by spokes 34. In the circumferential
direction the beams 32 are interconnected by sections 33. All the
cage forming truss sections are interconnected by conventional
means, for example, welding. The sections 33 function as stiffening
members and form, together with the longitudinal beams 32, an
octagonal cross-sectional shape of the cage. The apparatus further
comprises a plurality of wheel rim type members forming rings 36
which are secured to the longitudinal beams 32 by brackets 37 which
are slidably held in place by a form fit on axial guide rails 35
for axially locating the rings 36 along the length of the
longitudinal beams 32. Adjacent rings 36 are interconnected in the
axial direction by piston cylinders 36' for controlling the gap
width BSL shown in FIG. 3, and for closing the gap BSL. The carrier
plates 23 are secured to these rings 36 as mentioned above. The
radial adjustment cylinders 24 and the radial guide bushings 31 are
not shown in any detail in FIG. 4. However, FIG. 4 does show that
most carrier plates 23 are in the intermediate molding and curing
position 26 while only a few carrier plates 23a are shown in the
radially outer mold body mounting position 27. In the central lower
middle position of FIG. 4, three mold bodies 1 have already been
mounted to the respective carrier plate.
Depending on the type of structural component to be manufactured,
the mandrel or arbor 32a may have different diameters along its
length, for example, to form a conical configuration. In that case,
the rings 36 are adjustable relative to each other only within a
certain axial range in which the particular rings have the same
diameter. As mentioned, the radial adjustment cylinders 24 and the
radial guides 31 are secured to the rings 36. However, the manner
of attachment may be selected in accordance with individual
requirements. For example, in FIGS. 2 and 3 the members 24 and 31
are secured to the circumference of the respective rings 36,
whereas in FIG. 4, these members 24, 31 are secured to the sides of
the rings 36. In any event, the displacement of the carrier plates
23, 23a will always be in the radial direction for achieving the
above described different positions 25, 26, 27.
The above mentioned division using ninety-six mold bodies around
the circumference of the fuselage also results in ninety-six
stringers 20. With this division there will be forty-eight
cylinders 24 and forty-eight guide bushings 31 alternately
distributed around a respective ring 36 so that the angular
division will be 3.degree., 45 minutes between the radial axes of a
cylinder 24 and an adjacent radial guide bushing 31 on the same
ring 36. The cylinders 24 also alternate with guide bushings 31 in
the longitudinal, axial direction. Each carrier plate 23, 23a is
supported by a cylinder 24 and a guide 31. Due to the alternating
arrangement of cylinders and guides, it is possible to replace one
half of the number of cylinders by a respective number of the
mentioned guide bushings 31, thereby reducing the costs.
Due to the above mentioned overlapping edges 23' of the carrier
plate 23 it is possible that the portion of a carrier plate which
is supported by a guide rather than by a piston cylinder is driven
by the next adjacent cylinder located circumferentially around the
respective ring 36.
FIG. 5 shows a perspective overview of the apparatus according to
the invention, for manufacturing curved wall structural components
such as an aircraft fuselage. The apparatus comprises a scaffolding
40 to which the mandrel or arbor 32a is attached with its large
diameter end in a bending stiff manner. In the front part of FIG. 5
there is a further scaffolding 41 which supports the front end of
the arbor 32a by means of a mounting member 42. The front end of
the arbor 32a is closed by a cover 58 suitable for closing the
space inside the arbor in a pressure-tight manner. The mounting
member 42 permits detaching or disconnecting the front end of the
arbor from the scaffolding 41. A bandaging or winding apparatus 43
supported on rails 44 for travelling in the axial direction of the
arbor 32a surrounds the arbor and the mold bodies mounted thereon
for applying the planking 55 as will be described below. The
bandaging apparatus 43 is movable back and forth in the direction
of the arrow 45.
Additional scaffold frames 46 and 47 carry heatable mold shells 49
and 50 which are supported by piston cylinders 51, 52 respectively.
For example, twelve mold shells 49 and twelve mold shells 50 are
provided on each side. These mold shells are interconnected with
each other by conventional hinge elements 49' and 50' so that the
mold shells may be moved with the aid of the respective piston
cylinders 51, 52 into a mold bodies enclosing position. Hinge
barrels may be provided along the upper and lower edges of the mold
shells for interconnecting the mold shells carried on frame 46 with
the mold shells carried on frame 47. Both frames 46, 47 are movable
on rails 48 perpendicularly to the axial direction A.
The apparatus described will be used in the following manner for
manufacturing an aircraft fuselage. In the circumferential
direction the individual sections of the fuselage are seamless or
closed and the following steps will be performed substantially in
the stated sequence.
Step (a): Prepreg tapes 61 are wound or bandaged around the
surfaces 12a, 12b, 12c, and 12d to form at least one, preferably
several, layers of fiber composite material around the mold
bodies.
Step (b): The wound or bandaged mold bodies 1 are secured to the
carrier plates 23 on a first ring 36 whereby the carrier plates 23
are in the mounting position 25 shown in FIG. 2.
Step (c): The plates 23 and bodies 1 are moved into the molding
position 26, whereby the longitudinal sides of the mold bodies
contact each other to form the I-beams or stringers 20 shown in
FIG. 2. This radially inward movement exerts a sufficient pressure
on the fiber compound material for the subsequent curing and
bonding.
Step (d): Mounting further bandaged mold bodies 1 on the carrier
plate 23 of the next ring 36.
Step (e): Moving the carrier plates of the next ring 36 into the
molding position 26, whereby the above mentioned gap BSL is
initially provided between the end surfaces of two mold bodies in
the axial direction.
Step (f): The rib reinforcing belt segments 28 are now inserted
into the gaps BSL as shown in FIG. 3. It should be noted here, that
the belt segments 28 may also be attached to an axial end of the
first group of mold bodies even before the second group of mold
bodies is mounted on the carrier plates of the next adjacent ring.
In any event, when the segment belts 28 are in place, the next step
is performed.
Step (g): Moving the second ring closer to the first ring 36 with
the aid of the piston cylinders 36' to remove the gap BSL and press
the belt segment 28 into place as shown in FIG. 3 at the left and
right ends in FIG. 3.
Step (h): Attaching or mounting the mold bodies 1 to the carrier
plates 23 of the third ring with the plates being in the radially
outward position 25.
Step (j): Inserting the belt segment 28 into the next gap and so
forth until the entire body section has been completed as just
described.
Step (k): Bandaging the mold bodies and thus the fuselage with
prepreg bands, thereby using the winding apparatus 43 which has a
component of conventional construction travelling all around the
fuselage to apply the planking 55. For this purpose the prepreg
band is mounted as a coil in the bandaging or winding apparatus 43
and that coil travels around the fuselage.
Step (1): The scaffold frames 46 and 47 are now moved toward the
fuselage and the molding shells 49, 50 are pressed against the
planking 55. The winding or bandaging apparatus 43 has been moved
out of the way for this purpose, for example, all the way close to
the scaffold 40 at the far end of the mandrel 32a.
Step (m): The piston cylinders 24 are now operated for moving the
carrier plates 23 into the position 27 shown in FIG. 2, whereby the
snap-in connections between the carrier plates 23 and the mold
bodies 1 are centrally released by pressurized air, for example,
since the mold bodies stay in place until the curing and bonding is
completed.
Step (n): The arbor 32a with the carrier plates 23 is moved out of
the structural component. For this purpose the mounting member 42
is disconnected from the front end of the arbor. The mold bodies 1
still remain in place since the molding shells 49, 50 hold the
structure in place and the mold bodies cannot move radially
inwardly.
Step (o): Insertion, if desired, of reinforcing strips 56 of fiber
composite material to strengthen the inner flange 22a of the
stringers 20.
Step (p): Rubber sheets are inserted into the structure to cover
all surfaces.
Step (q): The space between the mold bodies 1 mold shells 49, 50
and the rubber sheets is evacuated for avoiding air bubbles inside
the fiber composite material.
Step (r): The mold shells 49 and 50 are now heated.
Step (s): Compressed air is introduced inside of the structure and
the rubber sheets are pressed against the mold bodies 1 and mold
bodies 1 against mold shells 49, 50 by compressed air.
Step (t): The structural component is now cured in accordance with
the requirements for the particular prepreg material. These
requirements are usually furnished by the manufacturer of the
prepreg fiber composite material.
Step (u): The heating of the mold shells 49, 50 is switched off and
the cooling takes place as well as the removal of the compressed
air.
Step (v): The mold bodies are now removed from the structural
component as described above.
The mold shells 49, 50 of FIG. 5 are also made of fiber compound
material, for example by a manufacturing method as described in the
above mentioned related disclosure. The shape of the mold shells
determines the outer contour of the three-dimensional aircraft
fuselage. These shells and the frames 46, 47 take up the inner
pressure which is applied during the curing when the space between
the rubber sheets inside the structural component and the mold
bodies is pressurized. Thus, these shells 49, 50 are rigidly
interlocked around the circumference of the structural component,
for example by the above mentioned hinge members 49', 50'. It has
been found that the fiber compound material of the shells 49, 50 in
combination with the interlocking provides the required stiffness
or rigidity that these shells must have in order to assure the
dimensional stability, particularly the proper outer diameter of
the structural components, irrespective of the internal pressure
and irrespective of the heating during the curing and bonding. Both
ends of the inner space are closed by cover members of which the
front cover member 58 is shown in FIG. 5. These cover members are
connectable to the shells 49 and 50 by means not shown, but of
conventional construction. Thus, the apparatus itself forms the
autoclave for the curing and bonding. This feature is a substantial
saving because autoclaves of the sizes here involved are very
expensive.
FIG. 6 shows a portion of the structural component in this case of
an aircraft fuselage after the arbor 32a has been removed. In this
condition the inner surfaces of the mold bodies 1 are accessible.
The outer planking 55 has been applied and the mold shells 49 and
50 are pressing radially inwardly against the planking 55. The
shells 49, 50 are not shown in FIG. 6. At this time the reinforcing
belts 56 of prepreg fiber composite material are inserted to cover
the stringer flanges 22a through the openings 70 mentioned above.
The tool 57, such as a triangular section of metal may be used for
pressing the belts 56 in place. If desired, further reinforcing
belts 58' also of prepreg material are attached to the radially
outer facing flanges 22 of the stringers 20 prior to the winding of
the outer planking 55.
When the insertion of the belt 56 is completed, the inner surfaces
of the mold bodies 1 and of the supporting tools 57 are covered
with large surface area rubber sheets as mentioned above. These
sheets are then closed tightly all around so that the space between
the mold bodies and these sheets can be either evacuated or
pressurized. When the space is pressurized the sheets form a bubble
inside the structural component, whereby all elements that need to
be bonded to each other are exposed to a compression during the
curing which may be controlled by the pressurized air supplied into
the bubble. As mentioned, the space should preferably be first
evacuated prior to pressurizing so as to avoid the formation of air
bubbles inside the fiber composite material.
Generally, the temperature for the curing will be approximately
125.degree. C. and the pressure will be about 7 bar during the
curing. The curing time will depend on the thickness of the
structural elements to be bonded to each other and will normally be
within the range of three to five hours. After the curing and
hardening, the temperature is gradually reduced in accordance with
a predetermined cooling speed whereupon the space inside the rubber
sheets is again vented to the atmosphere.
Upon completion of these steps the rubber sheets are removed and
the mold bodies or rather, the mold members are also removed, for
example, by reaching into the handle holes 71. The removal has been
described in detail above. The upper portion of FIG. 6 shows the
structural component after the removal of the mold bodies. The
lower portion still shows the mold bodies prior to removal.
As shown in FIG. 3, the belt segments 28 for reinforcing the ribs
have a radial height HS corresponding to a multiple of the radial
height of the ribs shown approximately at 64' in FIG. 1c. A useful
range for the radial height of the belt segment 28 would be 1.5 to
6 times the height 64' of the ribs or of the height of the
stringers 20.
After completion of the mold body removal, the structural component
is supported, for example, by an overhead crane and thereafter, the
mold shells 49, 50 are removed prior to any further manufacturing
steps not related to the present invention.
Zones of the fuselage where external forces will be introduced into
the planking 55 of the fuselage may be reinforced by additional
fiber layers. For this purpose, the form bodies in the respective
zones are provided with depressions or cut-outs into which these
additional layers may be inserted. Similar reinforcements are
provided around openings in the fuselage, for example, as shown at
72 in FIG. 5, such as window or door openings. Preferably, these
openings are cut into the fuselage after the curing and then
reinforced. However, other reinforced zones may be provided by
inserting respective layers into recesses in mold bodies 1 for
curing with the entire structure.
One example of also reinforcing the planking 55 is shown at 58'
where the respective belts reinforce the flanges 22 of the
stringers 20 as well as the planking 55.
Rather than wrapping or winding the planking 55 as described above
with reference to the winding apparatus 43, it is possible to form
the planking 55 by overlapping rings having a zero pitch or by
using overlapping longitudinal strips or layers of fiber composite
material. A crosswise application of the fiber layers employing
strips running longitudinally and circumferentially may also be
employed. Rather than running a coil of prepreg tape with the
apparatus 43 around the structural component, it is possible to
instead rotate the structural component about its longitudinal axis
A, whereby the prepreg tape material is pulled off a supply coil.
This latter operation is suitable, especially for smaller aircraft
fuselages and has the advantage of reducing costs.
Depending on the size of a structural component, it will generally
be possible to construct such components in a seamless manner.
However, under certain circumstances it may be practical to divide
the entire fuselage into two or more half shells or sections which
are manufactured as described herein and then interconnected along
a seam by conventional means.
Although the invention has been described with reference to
specific example embodiments, it will be appreciated, that it is
intended to cover all modifications and equivalents within the
scope of the appended claims.
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